Best Particle Therapy, Inc. is a relatively new member of the TeamBest® family of companies,
founded by Krishnan Suthanthiran
in 1977. TeamBest® currently
offers products for brachytherapy and teletherapy.
Best NOMOS, a TeamBest®
company, invented IMRT (intensity-modulated radiation therapy) in the early 1990s.
TeamBest® continues to expand its product offerings to cover
low tech to high tech with the primary goal of making these technologies affordable and accessible
globally. Best Particle Therapy will utilize
advanced state-of-the-art accelerator technologies and provide cost-effective solutions for
particle therapy treatment and research.

Introduction to Particle Therapy

“Particle Therapy” (PT) is a radiotherapy technique that utilizes hadrons
and was first proposed by R.R.Wilson
in 1946 after analysis of inverted depth-dose distribution measured at the Berkeley Cyclotron.
This analysis resulted in the first radiological use of hadrons in 1954 by Cornelius Tobias
and John Lawrence at the Radiation Laboratory (former E.O. Lawrence Berkeley National Laboratory,
LBNL). This pioneering work explored the use of hadrons, i.e., protons, deuterons, helium and
neon ions, for therapeutic exposure of human patients and concluded at LBNL with the shutdown
of the BEVALAC in 1992. Inspired by the success of the early work in the USA, international
efforts were made to develop particle therapy into a mature radiological treatment modality.

The following illustration summarizes the different types of radiation used
in various radiotherapy techniques. The different types of radiation are characterized as photons
or charged particles.

Illustration courtesy of Dr. Hirohiko Tsujii, MD

The most common
internal and
external radiotherapy techniques
utilize X-rays and gamma rays, both of which are identical to photons with extremely short
wavelengths capable of causing ionization and are therefore called ionizing radiation.
It is worth mentioning that gamma rays are, in fact, identical to X-rays but have been given
a unique name to identify them as originating from nuclear decay.

Why Particle Therapy?

Because protons and carbon ions have mass unlike photons, a charged particle is characterized
by an inverted depth-dose distribution (the so called Bragg peak), which is most favorable for
deep-seated target volumes. The main criterion used in all radiotherapy techniques is to deliver a
sufficient dose to achieve tumor control while minimizing side effects. This challenge requires
an ongoing understanding of the biological effectiveness, as well as high precision in conformity.
While X-rays and protons have similar Relative Biological Effectiveness (RBE), protons offer the
physical advantage of having a limited penetration depth governed by the laws of physics.
The actual range at which the particle stops is strictly dependent on the kinetic energy
of the particle, and therefore facilitates the possibility of a treatment plan without any
significant distal dose. Quite often pristine Bragg peaks are presented to illustrate
advantages of particle therapy; however, such pristine depth-dose distributions have
little value in practice since a Spread Out Bragg Peak (SOBP) after range stacking is
necessary to fill in a tumor volume. The dose distributions for X-rays and SOBP for
protons and carbon ions are shown below after considering biological effects.

Dose Distribution of Radiation Considering Biological Effects

Illustration courtesy of Dr. Hirohiko Tsujii, MD

The dose distributions clearly illustrate the advantages associated with particle therapy
by the elimination of the distal dose. It is worth pointing out that X-rays can often achieve
excellent conformity using IMRT techniques or implanting very low energy gamma ray sources;
but the unmistakable advantage of particle therapy is associated with precise control of
particle penetration depth.

Advantages of Carbon Ions in Particle Therapy

Because of the greater mass
of carbon ions, multiple scattering and range straggling is approximately 3 times less than protons,
resulting in a sharper lateral and longitudinal edge; it is therefore ideal for treatment of deep-seated
tumors, where penumbra becomes a limiting factor.

Since the Linear Energy Transfer (LET)
in the peak of a carbon beam is larger than that of photon and proton beams, the Relative
Biological Effectiveness (RBE) is 2 to 3 times greater for carbon ions. Therefore, carbon
ions have enhanced therapeutic benefits in treating radiation-resistant tumors.

Fragmentation of carbon ions produce a tail
in the dose distribution after the Bragg peak (see illustration), which contributes to a small
but finite distal dose. These carbon fragments can be a nuisance in certain cases; however,
they are also indicative of the production of a large number of in-situ positron emitters
throughout the entire treatment volume. In comparison with proton therapy, carbon therapy
results in a greater level of detectable activation with less uncertainty, facilitating
online monitoring with PET and the advantage of 3D treatment verification.

Best Particle Therapy will deliver energetic particle
beams of protons and carbon ions with the highest level of precision to treat deep-seated as
well as radiation-resistant tumors.